Vessel hull configuration

ABSTRACT

A vessel ( 10 ) comprising a hull ( 15 ) having a the Longitudinal Centre of Flotation (LCF) at the design load waterline ( 25 ) at rest with a value of less than about 35% of the vessel waterline length measured from the aftermost point ( 19 ) of the vessel waterline. The design vessel speed at design load waterline is at or above Froude Number of 0.45. The hull ( 15 ) has a length-to-beam ratio on the design waterline of greater than about 8.0. The Longitudinal Centre of Buoyancy (LCB) is between about 30% and 45% of the vessel waterline length measured from the aftermost point ( 19 ) of the vessel waterline ( 25 ). In one arrangement, the vessel ( 10 ) may comprise a single hull vessel. In another arrangement, the vessel ( 10 ) may comprise a multi-hulled vessel.

FIELD OF THE INVENTION

This invention relates to marine vessels particularly sea-going vesselsfor commercial or military use.

The invention has been devised particularly, although not solely, as amulti-hulled vessel configured as a trimaran comprising a centrallylocated main hull and two side hulls.

BACKGROUND ART

The following discussion of the background art is intended to facilitatean understanding of the present invention only. The discussion is not anacknowledgement or admission that any of the material referred to is orwas part of the common general knowledge as at the priority date of theapplication.

A conventional sea-going vessel for commercial or military use isgenerally designed such that resistance to forward motion in a calm seais minimised with a view to optimising fuel efficiency. The shape of thehull is significant in relation to minimisation of drag, and the driversof the ideal shape are generally well understood by those skilled in theart.

One of these drivers of optimum performance is the length of thewaterline of the vessel, which should ideally be as long as practical.This is also desirable to minimise the vessel motions and to provide acomfortable ride. However a longer vessel involves a greaterconstruction cost, and generally the extra length is not justified.

Another driver is the location of the centre of the immersed hull volumerelative to the length of the vessel. The location is termed theLongitudinal Centre of Buoyancy (LCB), and experience has shown that fora low resistance it should be ideally located between 48% and 53% of thevessel length measured from the after end of the water line length ofthe vessel (for example Saunders H. E. “Hydrodynamics in Ship Design”,Society of Naval Architects and Marine Engineers SNAME, New York, USA).

Another term used by those knowledgeable in the art, is the waterplanearea, which describes the footprint of the vessel on the surface of thewater. The centroid of this shape, the waterplane area, is called theLongitudinal Centre of Flotation (LCF).

On most conventional sea-going vessels, the LCF value is approximatelysimilar to the LCB value, being within 5% at normal vessel draughts.Typically, the LCF value is between 43% and 53% of the vessel lengthmeasured from the after end of the water line length of the vessel.

FIGS. 1 and 2 of the drawings illustrate LCB and LCF positions ofconventional hull configurations. FIG. 3 is a view corresponding to FIG.1 for a three-hulled vessel.

In FIGS. 1 and 2, the vessel depicted comprises a hull 1 having a bow 2and a stern 3. The design waterline is represented by the line denotedby reference numeral 4 and has length L. The LCB is denoted by referencenumeral 5 and the LCF is denoted by reference numeral 6.

In FIG. 3, the vessel is of three-hull configuration comprising acentrally located main hull 1 and two side hulls 7. The design waterlineLCF have corresponding reference numerals to those used for the hullshown in FIGS. 1 and 2. The design waterline 4 is also shown for eachside hull 7.

At high speed, typically above approximately 30 knots, the resistanceand comfort factors dominate the design process. Additional vessellength becomes desirable in order to maximise speed for the availablepower, or to conversely reduce the power and hence fuel consumption fora given speed. A longer vessel will also generally have a lesserpitching, heave and yaw motions.

A three-hulled vessel, having a main central hull with two amahs or sidehull is disclosed in U.S. Pat. No. 6,736,080 (Armstrong). This type ofvessel arrangement can usefully benefit from additional length whendesigned for high speed.

When the three-hulled arrangement is designed for a high-speed ferryuse, it is desirable to moor the vessel stern-on and to provide a widestern such that the loading and unloading process can be rapidlyachieved, as discussed in U.S. Pat. No. 5,269,245 to Bystedt andToreskog.

It is against this background that the present invention has beendeveloped.

DISCLOSURE OF THE INVENTION

According to a first aspect of the invention there is provided a vesselcomprising a hull having an LCF at the design load waterline at restwith a value of less than about 35% of the vessel waterline lengthmeasured from the aftermost point of the vessel waterline.

Preferably, the LCF is between about 30% and 34% of the vessel waterlinelength measured from the aftermost point of the vessel waterline.

Preferably, the design vessel speed at design load waterline is at orabove Froude Number of 0.45.

Preferably, the main hull has a length-to-beam ratio on the designwaterline of greater than about 8.0.

Preferably, the slenderness ratio of the vessel, described as the lengthon the design waterline divided by the cube root of the volume ofdisplacement in consistent units, is greater than 7.0.

Preferably, the vessel waterline length is between 24 metres and 250metres.

Preferably, the LCB is between about 30% and 45% of the vessel waterlinelength measured from the aftermost point of the vessel waterline.

More preferably, the LCB is between 34% and 42% of the vessel waterlinelength measured from the aftermost point of the vessel waterline

The vessel may comprise a single hull vessel.

The vessel may comprise a multi-hulled vessel. The multi-hulled vesselmay be configured as a trimaran comprising a centrally located main hulland two side hulls, wherein the main hull constitutes the hull inaccordance with the invention.

The trimaran may be configured as a ferry.

According to a second aspect of the invention there is provided atrimaran comprising a main hull and two side hulls, the main hull havinga LCF at the design load waterline at rest with a value of less thanabout 34% of the vessel waterline length measured from the aftermostpoint of the vessel waterline.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the followingdescription of one specific embodiment thereof. The description will bemade with reference to the accompanying drawings in which:

FIG. 1 is a schematic plan view of the waterline of a conventional hullconfiguration, illustrating the LCF position;

FIG. 2 is a schematic side view of a conventional hull configuration,illustrating the LCF and LCB positions;

FIG. 3 is a view similar to FIG. 1 but for a conventional three-hullconfiguration;

FIG. 4 is a schematic perspective underside view of the hullconfiguration of a three-hulled vessel according to the embodiment;

FIG. 5 is a schematic plan view of the waterline of a conventional hullconfiguration, illustrating the LCF position; and

FIG. 6 is a schematic side view of the main hull of the three-hulledvessel according to the embodiment, illustrating the LCF and LCBpositions.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

The embodiment shown in FIGS. 4 and 5 of the drawings is directed to amulti-hulled vessel 10 according to the embodiment. In the arrangementshown, the vessel 10 comprises a three-hulled vessel (being a trimaran)configured as high speed commercial or military vessel, such as a ferry,for passenger and cargo transport, including vehicle transport.

Typically, the trimaran 10 has a waterline length between 24 metres and250 metres, although it is of course not limited thereto.

The triamaran 10 comprises an understructure 11 and a superstructure(not shown), both constructed primarily of aluminium. The waterline inrelation to the understructure 11 is identified in FIG. 3 by referencenumeral 13.

The under structure 11 comprises a centrally located main hull 15 andtwo laterally spaced side hulls 16 commonly known as amahs.

The main hull 15 has a forward end terminating at a bow 17 and an aftend terminating at a stern 19. The bow 17 may incorporate a forwardlyextending bulbous portion 21 below the waterline 13.

The design waterline of the main hull 15 is represented by the linedenoted by reference numeral 23 and has length L. The design waterlinefor each side hull 16 is represented by the line denoted by referencenumeral 25. The LCB is denoted by reference numeral 27 and the LCF isdenoted by reference numeral 29.

The superstructure (not shown) is configured such that the majority ofthe weight of the vessel lies in the after part of the vessel (aft ofcentre of the vessel measured along the waterline length), which for alevel trim implies that the centre of buoyancy is also aft of amidships.Such an arrangement allows the vessel to be moored stern-on and providesa wide stern such that the loading and unloading process can be rapidlyachieved.

The main hull 15 extends forwardly beyond the useful cargo areas andespecially the passenger cabin, in order to provide the longestpractical hull within financial constraints.

By virtue of being constructed in accordance with the invention, themain hull 15 is designed for, and facilitates, implementation of thissuperstructure configuration.

Specifically, the trimaran 10 has a Froude Number of greater than 0.45and the main hull 15 has a length-to-beam ratio on the design waterlineof greater than 8.0.

The main hull 15 has a LCB lying between 34% and 42% of the vesselwaterline length measured from the aftermost point of the vesselwaterline 23 which is represented by the value L. This position of theLCB is considerably further aft than the value used for the design ofmore convention vessels, as depicted in FIGS. 1, 2 and 3.

The main hull 15 also has a LCF at the design load waterline at restwith a value of less than about 35% of the vessel waterline length Lmeasured from the aftermost point of the vessel waterline. Moreparticularly, the LCF is preferably between about 30% and 34% of thevessel waterline length L.

This hull configuration offers relatively low resistance and also thepossibility of improved comfort from the reduction of verticalacceleration.

The LCB and LCF values described above are for the vessel floating atleast at the design load waterline.

From the foregoing, it is evident that the present embodiment provides avessel with a hull configuration which delivers improved performancewhile also accommodating a superstructure configured such that themajority of the weight of the vessel lies in the after part of thevessel. Such an arrangement allows the vessel to be moored stern-on andprovides a wide stern such that the loading and unloading process can berapidly achieved. Further, the centre hull extends forward beyond theuseful cargo areas and especially the passenger cabin, in order toprovide the longest practical hull within financial constraints.

It should be appreciated that the scope of the invention is not limitedto the scope of the embodiment described, and that various changes andmodification may be made without departing from the scope of theinvention.

While the embodiment has been described in relation to three-hullvessel, it should be understood that it may also be applicable to otherhull configurations, including for example a single-hull configuration,a double-hull configuration (being a catamaran), and a pentamaran.

Throughout the specification and claims, unless the context requiresotherwise, the word “comprise” or variations such as “comprises” or“comprising”, will be understood to imply the inclusion of a statedinteger or group of integers but not the exclusion of any other integeror group of integers.

1.-14. (canceled)
 15. A vessel comprising a hull having a LCF at adesign load waterline at rest with a value of less than about 35% of thevessel waterline length measured from the aftermost point of the vesselwaterline, wherein a design vessel speed at design load waterline is ator above Froude Number of 0.45, wherein the hull has a length-to-beamratio on the design waterline of greater than about 8.0, wherein thevessel is configured as a trimaran comprising a centrally located mainhull and two side hulls, and wherein the main hull constitutes saidhull.
 16. The vessel according to claim 15 wherein the LCF is betweenabout 30% and 34% of the vessel waterline length measured from theaftermost point of the vessel waterline.
 17. The vessel according toclaim 15 wherein a slenderness ratio of the vessel, described as thelength on the design waterline divided by the cube root of the volume ofdisplacement in consistent units, is greater than 7.0.
 18. The vesselaccording to claim 15 wherein the vessel waterline length is between 24metres and 250 metres.
 19. The vessel according to claim 15 wherein theLCB is between about 30% and 45% of the vessel waterline length measuredfrom the aftermost point of the vessel waterline.
 20. The vesselaccording to claim 19 wherein the LCB is between 34% and 42% of thevessel waterline length measured from the aftermost point of the vesselwaterline.
 21. The vessel according to claim 15 configured as a ferry.